It is generally known that rotation of a substrate during vapor plating, vapor deposition or sputtering is desirable to promote uniformity in the surface treatment. For example, in U.S. Pat. No. 3,983,838 there is disclosed a planetary evaporator wherein substrates are turned during surface treatment. This patent as well as others teach the need for circular rotation of a substrate.
Most prior devices for treating substrates do so in a cylindrical enclosure in which the substrates are rotated within the inner periphery of the cylinder. This limits the throughput of the system and essentially treats batches of substrates. Others have recognized this and have provided linear or in-line systems wherein wafers are loaded into one end of the system and traverse a linear path, emerging at the opposite end of the system. Such an apparatus is shown in U.K. patent application No. 2,095,704 A. In such linear systems, it has been previously recognized that rotation of the substrate during surface treatment is desirable. An example of a carrier with means for rotating individual substrates is shown in U.K. patent application No. 2,135,700 A.
An object of the invention was to provide a means for rotating a plurality of wafers traveling through an in-line surface treatment system, such as a sputtering system.